Liquid crystal displays (LCDs) are used in portable computers and other electronic devices to display information. LCDs modulate light to create images using selectively transmissive and opaque portions of the display, the selection being controlled by passing electric current through the liquid crystal material. Transmissive-type LCDs are illuminated by an artificial backlight positioned behind the LCD glass to provide the contrast between the light transmissive and opaque portions of the display. An undesirable characteristic of such LCDs is that they typically take a long time to warm up. During its warm-up period, the visibility of an LCD is usually inadequate, due to the low contrast ratio between the light transmissive and opaque portions thereof.
To remedy the visibility problem encountered during LCD warm-up, users will often attempt to counteract the problem by manually increasing the brightness level of the LCD, using a brightness control knob, for example, to a maximum level. Although this does substantially increase the visibility of the LCD, this solution is deficient in that the user will often neglect to return the brightness back to a normal level once the LCD has completely warmed up. Continuous use of the PC with the LCD at maximum brightness consumes a large amount of power and results in the battery of the PC being depleted much more quickly than desired. For example, in a particular portable PC in which the LCD has sixteen different "brightness" levels, operating the PC with the LCD brightness control set to level sixteen consumes twice as much power than if the PC were operated with he LCD brightness control set to level fourteen.
Therefore, what is needed is a system for automatically increasing the visibility of an LCD during warm-up thereof without substantially increasing the amount of power consumed by the LCD after it has warmed up.